Environmental factors such as rain or other forms of precipitation can attenuate wireless communication including microwave communication. Rain drops can be less than 2 mm or even greater than 5 mm. Larger rain drops tend to attenuate wireless communication more than smaller rain drops. The size of rain drops is approximately in the same scale as λ/4 of microwave signals.
Wireless communication over multiple polarizations may experience greater attenuation on one polarized signal than on another polarized signal, especially during rain. Rain drops are often pancake shaped and not spherical, such that they have a horizontal cross-sectional area that is greater than a vertical cross-sectional area. The bigger the size of rain drops in a dimension perpendicular to the polarization, the more attenuation will be experienced. Thus, a horizontally-polarized signal may be attenuated by rain more than a vertically-polarized signal due to the rain drops being pancake shaped.